_require "basis.smi"
structure Tree =
struct
  datatype tree =
      ND of {left:tree, next:tree ref, prev:tree ref, right:tree, sz:int,
             x:real, y:real}
    | NULL
  val mkNode : tree * tree * real * real * int -> tree
  val printTree : TextIO.outstream * tree -> unit
  val printList : TextIO.outstream * tree -> unit
end
